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idiopathic hypersomnia

The journey of a marathon sleeper

A marathon sleeper who got away left some clues for Emory and University of Florida scientists to follow. What they found could provide benefits for patients with the genetic disease myotonic dystrophy (DM) and possibly the sleep disorder idiopathic hypersomnia (IH).

The classic symptom for DM is: someone has trouble releasing their grip on a doorknob. However, the disease does not only affect the muscles. Clinicians have recognized for years that DM can result in disabling daytime sleepiness and sometimes cognitive impairments. At the Myotonic Dystrophy Foundation meeting in September, a session was held gathering patient input on central nervous system (CNS) symptoms, so that future clinical trials could track those symptoms more rigorously.

Emory scientists are investigating this aspect of DM. Cell biology chair Gary Bassell was interested in the disease, because it’s a triplet repeat disorder, similar to fragile X syndrome, yet the CNS mechanisms and symptoms are very different. In DM, an expanded triplet or quadruplet repeat produces toxic RNA, which disrupts the process of RNA splicing, affecting multiple cell types and tissues.

Rye at San Francisco myotonic dystrophy meeting. Photo courtesy of Hypersomnia Foundation.

Neurologist and sleep specialist David Rye also has become involved. Recall Rye’s 2012 paper in Science Translational Medicine, which described a still-mysterious GABA-enhancing substance present in the spinal fluid of some super-sleepy patients. (GABA is a neurotransmitter important for regulating sleep.)

In seven of those patients, his team tested the “wake up” effects of flumazenil, conventionally used as an antidote to benzodiazepines. One of those patients was an Atlanta lawyer, whose recovery was later featured in the Wall Street Journal and on the Today Show. It turns out that another one of the seven, whose alertness increased in response to flumazenil, has DM.

In an overnight sleep exam, this man slept for 12 hours straight – the longest of the seven. But an IH diagnosis didn’t fit, because in the standard “take a nap five times” test, he didn’t doze off very quickly. He became frustrated with the stimulants he was given and sought treatment elsewhere, Rye says. Lab Land doesn’t have all the details of this patient’s history, but eventually he was diagnosed with DM, which clarified his situation. Read more

Posted on by Quinn Eastman in Neuro Leave a comment

Imaging sleep drunkenness: #IHAW2017

At some point, everyone has experienced a temporary groggy feeling after waking up called sleep inertia. Scientists know a lot about sleep inertia already, including how it impairs cognitive and motor abilities, and how it varies with the time of day and type of sleep that precedes it. They even have pictures of how the brain wakes up piece by piece.

People with idiopathic hypersomnia or IH display something that seems stronger, termed “sleep drunkenness,” which can last for hours. Czech neurologist Bedrich Roth, the first to identify IH as something separate from other sleep disorders, proposed sleep drunkenness as IH’s defining characteristic.

Note: Emory readers may recall the young Atlanta lawyer treated for IH by David Rye, Kathy Parker and colleagues several years ago. Our post today is part of IH Awareness Week® 2017.

Sleep drunkenness is what makes IH distinctive in comparison to narcolepsy, especially narcolepsy with cataplexy, whose sufferers tend to fall asleep quickly. Those with full body cataplexy can collapse on the floor in response to emotions such as surprise or amusement. In contrast, people with IH tend not to doze off so suddenly, but they do identify with the statement “Waking up is the hardest thing I do all day.”

At Emory, neurologist Lynn Marie Trotti and colleagues are in the middle of a brain imaging study looking at sleep drunkenness.

“We want to find out if sleep drunkenness in IH is the same as what happens to healthy people with sleep inertia and is more pronounced, or whether it’s something different,” Trotti says. Read more

Posted on by Quinn Eastman in Neuro Leave a comment